1. Field of the Invention
The present invention relates to the field of telecommunications. More particularly, the present invention relates to a method and to a system for communicating between an airborne data terminal and a ground-based computer network.
2. Description of Related Art
The ability for passengers on a commercial airline flight to make phone calls is well-known. Initially, such airborne telephone calls utilized an analog technology that was similar to that used by an airborne radio station broadcasting a modulated voice signal over a designated frequency to a ground-based station. The ground station interfaced with a Public Switched Telephony Network (PSTN) to complete the call. The analog approach suffers from problems associated with signal degradation, and requires a relatively large bandwidth for carrying a voice band signal.
An all digital air-to-ground telephony network service was introduced in 1993 in which voice signals are carried by an ISDN link on an aircraft to a radio link. Modern digital transmission and speech processing techniques are used on the voice signals before an airborne radio transmitter transmits an encoded digital voice signal to the ground where the voice signal is routed to the PSTN. The digital approach delivers a clearer voice quality than the analog approach, and allows evolving speech encoding techniques to carry more simultaneous voice calls over available communication channels.
At the time the all digital air-to-ground service was introduced, the only data service envisioned was facsimile and data modem-type calls to be made to ground-based stations or terminals. To accommodate existing facsimile and data modems that might be used on an aircraft for sending facsimile documents or for retrieving e-mail messages, a voice encoder on the aircraft used for voice calls is bypassed with a proper rate adaptation so that modem signals are send over the radio link. Still, this type of connection is considered to be a circuit-switched voice call, that is, each dialup consumes one standard voice channel. As a result, the tariff for a conventional airborne data service call is the same as the tariff for a standard voice call because the procedure for setting up the two types of calls is the same, and the bandwidth that is consumed by a conventional airborne data call is the same as the bandwidth consumed by a standard voice call. Further, the types of data services that are conveniently available through conventional airborne data service calls are severely limited because of the limited bandwidth available for a conventional airborne data call. For example, conventional airborne data services do not provide a bandwidth that is sufficient for supporting, for example, access to the Internet in which graphics, audio, video, textual and multimedia content are available.
What is needed in a way to provide an integrated voice/data service to airborne passengers that can mix various data services, such as accessing the Internet or placing a voice call, and thereby utilize the limited air channels available to airborne passengers more efficiently.